pgsql: Support for MOVE in PL/PgSQL.

Log Message:
-----------
Support for MOVE in PL/PgSQL. Initial patch from Magnus, some improvements
by Pavel Stehule, and reviewed by Neil Conway.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        plpgsql.sgml (r1.108 -> r1.109)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml.diff?r1=1.108&r2=1.109)
    pgsql/src/pl/plpgsql/src:
        gram.y (r1.101 -> r1.102)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/gram.y.diff?r1=1.101&r2=1.102)
        pl_exec.c (r1.195 -> r1.196)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.195&r2=1.196)
        pl_funcs.c (r1.58 -> r1.59)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_funcs.c.diff?r1=1.58&r2=1.59)
        plpgsql.h (r1.87 -> r1.88)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/plpgsql.h.diff?r1=1.87&r2=1.88)
        scan.l (r1.56 -> r1.57)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/scan.l.diff?r1=1.56&r2=1.57)
    pgsql/src/test/regress/expected:
        plpgsql.out (r1.53 -> r1.54)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/plpgsql.out.diff?r1=1.53&r2=1.54)
    pgsql/src/test/regress/sql:
        plpgsql.sql (r1.46 -> r1.47)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/plpgsql.sql.diff?r1=1.46&r2=1.47)